The present invention relates generally to ground opener units for an agricultural implement and, more particularly, to an assembly for automatically and continually adjusting the down pressure applied to a set of disc openers ganged together in response to changes in soil conditions to maintain the set of discs at a relatively constant penetration depth so that the discs each cut an elongated trench in the soil at a substantially constant depth.
A planter generally consists of a toolbar that may be hitched to a tractor and a number of disc opener units mounted to the toolbar. The disc opener units have a disc or coulter that cuts a furrow into a field and a seed tube that deposits seed into the furrow. Some disc opener units are equipped with an additional tube for depositing fertilizer into the furrow. The depth at which the disc penetrates into the field and cuts the furrow is controlled by a gauge wheel. The position of the gauge wheel is typically set by rotating a lever or control arm to one of a series of depth setting positions. While the gauge wheel sets the penetration depth for the disc, a down pressure system, which typically includes a hydraulic cylinder, applies a down force on the disc to ensure that the disc penetrates into the ground. For most planters, the amount of down force can be adjusted by the operator to accommodate different soil conditions.
Notwithstanding the ability to vary the down force to changing soil conditions, many operators are unsure as to the appropriate down pressure setting for a given soil condition. As a result, many such operators will set the down pressure setting such that an excessive amount of down force is applied and leave the setting unchanged. Thus, unless extreme ground conditions are present, there will always be sufficient down force applied to the disc for the disc to penetrate to the desired cutting depth.
Constantly operating the planter with the down pressure system set to the maximal down pressure setting however can have detrimental effects. More specifically, since the excess down force is transmitted through the gauge wheel assembly, the gauge wheel, control lever, and/or gauge wheel bearings may fail premature if the down pressure system is always set to apply an excessive amount of down pressure.
Thus, there is a need for a down pressure control system that places less stress on the gauge wheel assembly while also applying a down force on the disc that accommodates a varying range of soil conditions.